One more attempt to fix #4867

lib/pure/osproc.nim

@@ -774,7 +774,10 @@ elif not defined(useNimRtl):
     data.workingDir = workingDir
 
     when useProcessAuxSpawn:
+      var currentDir = getCurrentDir()
       pid = startProcessAuxSpawn(data)
+      if workingDir.len > 0:
+        setCurrentDir(currentDir)
     else:
       pid = startProcessAuxFork(data)
 
@@ -835,7 +838,6 @@ elif not defined(useNimRtl):
           chck posix_spawn_file_actions_adddup2(fops, data.pStderr[writeIdx], 2)
 
       var res: cint
-      # FIXME: chdir is global to process
       if data.workingDir.len > 0:
         setCurrentDir($data.workingDir)
       var pid: Pid

tests/osproc/tworkingdir.nim

@@ -0,0 +1,16 @@
+discard """
+  file: "tworkingdir.nim"
+  output: ""
+"""
+
+import osproc, os
+when defined(windows):
+  # Windows don't have this issue, so we won't test it.
+  discard
+else:
+  let dir1 = getCurrentDir()
+  var process = startProcess("/usr/bin/env", "/usr/bin", ["true"])
+  let dir2 = getCurrentDir()
+  discard process.waitForExit()
+  process.close()
+  doAssert(dir1 == dir2, $dir1 & " != " & $dir2)